We built the countertop for this project so I don't have any direct experience with use. However, we took these pictures a year after the wood top and beadboard back splash were installed and everything (as the pictures show) was/is in very nice condition.

Water intrusion/problems are a legitimate concern for any wood product. The amount of water necessary to negatively affect finished wood pieces (key word is finished) would be significant. Simply water spray from average use of your sink faucet shouldn't cause any problems for either material, and would advise you to seek a wet-area or waterproof-type finish for your back splash. I can say definitively that our permanent finish is 100% waterproof and can handle much more water without any affects.

I hope this helps.